Support Structure for a Medicament
A support structure (1) for a medicament comprising a base (2) with at least one cavity (3) for the medicament and a lid (4) for sealing the medicament within the cavity (3). Each moisture permeable region of the structure (6) is protected against the ingress of mositure by a moisture absorbing sink (7) between that region and the ambient air outside the structure (1).
The present invention relates to a support structure for a medicament in the form of, for example, a blister pack for a drug or an injection moulded drug dosing element as used in an inhalation device. A typical blister pack for a medicament is described in WO 01/45777 and a typical drug dosing element is described in U.S. Pat. No. 5,590,645.
With powdered medicaments there is a demand for a package/support structure which is able to keep the powder free from the ingress of moisture both during storage and when the powdered medicament has been loaded into a delivery device. Similarly, if the drug is in tablet or capsule form there is also a demand to keep the tablets/capsules, which are typically held in a blister pack, free from the ingress of moisture. The main weakness in a support structure which has a lid sealed to a base, having one or more cavities for holding the medicament, is in the region where the lid is sealed to the base. If the support structure is in the form of a blister pack, the lid and base are often both made from a material having an aluminium layer which makes these elements moisture impermeable. Accordingly, the only region where moisture can penetrate the blister pack is through the lid sealing region which is typically a heat seal. If the base of the blister pack is made from a plastic material then there will also be moisture ingress through the base material to the medicament. If the support structure is in the form of an injection moulded dosing element, the injection moulded base will be made from a moisture permeable material whereas the lid will typically have an aluminium layer making it moisture impermeable. In this case, there will also be moisture ingress through both the heat seal between the lid and base and through the base material.
The problem of moisture ingress has been overcome to a certain degree in prior art inhalation device components by using aluminium containing foil materials for both the lid and base and spacing adjacent cavities by approximately 3 mm. With such a construction, moisture within an empty cavity does not then compromise an adjacent cavity which still contains a dose of medicament. The only weakness resides in the heat seal between lid and base. A disadvantage with this construction is that there is a limit to the number of doses which can be arranged on the blister pack/dosing element due to the spacing requirement.
Other prior art solutions include providing a desiccant source which is connected to or placed within a cavity containing the medicament. However, this solution is reactive only, in that moisture is removed after having penetrated a cavity rather than preventing moisture from entering the cavity in the first place. Similarly, an alternative solution has been to use a desiccant box inside an aluminium bag which holds a plurality of medicament doses, e.g., tablets, but this form of moisture protection is destroyed when the bag is opened for the first time so that there is no in-use stability. For further examples of prior art solutions, reference should be made to WO 03/61742 and U.S. Pat. No. 6,132,394.
In view of the problems discussed above, the present invention seeks to provide moisture protection for the medicament and to maximise the number of doses arranged on the support structure.
According to the present invention, there is provided a support structure for a medicament comprising a base with at least one cavity for the medicament and a lid for sealing the medicament within the cavity characterised in that each moisture permeable region of the structure is protected against the ingress of moisture by locating a moisture absorbing sink between that region and the ambient air outside the structure.
Preferably, the sink reduces the relative humidity (RH) of the air passing through it to substantially the relative humidity (RH) of the air within the cavity so that there is minimal diffusion of moisture from the sink to the cavity.
Preferably, each moisture permeable region comprises an inner moisture permeable barrier located adjacent to the cavity and an outer moisture permeable barrier, the moisture absorbing sink being located between the inner and outer barriers.
Preferably, the base and the lid are moisture impermeable and the moisture permeable region of the structure is located where the lid is sealed to the base.
Preferably, the moisture absorbing sink between the lid and the base is spaced from the periphery of the cavity thereby forming an inner moisture permeable region and an outer moisture permeable region, the sink breaking the moisture ingress path so that there is minimal diffusion of moisture through the inner moisture permeable region to the cavity.
Preferably, the moisture absorbing sink comprises a channel in the base surrounding the cavity which contains dry air.
Preferably, there is provided a plurality of cavities each having a channel filled with dry air.
Preferably, each channel is connected to a single desiccant source which dries the air in all the channels.
Preferably, the moisture absorbing sink comprises a polymer ring surrounding the cavity and located between the lid and the base.
Preferably, there is further provided a plurality of cavities each having a polymer ring.
Preferably, the base and the lid have an aluminium layer for moisture impermeability, the lid being heat sealed to the base.
Preferably, the lid is moisture impermeable and the base material is moisture permeable, the moisture permeable regions being located where the lid is sealed to the base and within the base material of the cavity walls.
Preferably, a first moisture absorbing sink is located between the lid and the base and is spaced from the periphery of the cavity and a second moisture absorbing sink is located within the base material of the cavity walls thereby forming inner moisture permeable barriers and outer moisture permeable barriers, the sink breaking the moisture ingress path so that there is minimal diffusion of moisture through the inner moisture permeable barriers to the cavity.
Preferably, the moisture absorbing sink comprises a channel containing dry air surrounding the cavity opening where the lid is sealed to the base and passing through the cavity walls.
Preferably, there is further provided a plurality of cavities each having a channel containing dry air.
Preferably, each channel is connected to a single desiccant source which dries the air in all the channels.
Preferably, the base is injection moulded and the lid has an aluminium layer for moisture impermeability, the lid being heat sealed to the base.
Preferably, the base comprises cooperating stackable elements, each element having a plurality of cavities, the cavities within one of the elements sitting between the cavities within another element when stacked, a moisture absorbing sink being formed by the spacing between the cooperating elements.
Preferred embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, of which:
Reference should now be made to
In the present invention, it is proposed to locate a moisture absorbing sink between each moisture permeable region of the support structure and the ambient air. This can be achieved, for example, by breaking the single barrier into an outer barrier and an inner barrier with the sink located between the two barriers.
Reference should now be made to
In
The base 102 of the dosing element 101 would typically be injection moulded and hence would be moisture permeable. With this arrangement, moisture protection is needed both where the lid 104 is heat sealed to the base 102 and within the base material. There are channels 107 running between adjacent cavities and beneath each cavity through the base 102.
The channels 107 all connect to a desiccant 108 which dries the air in the channels to reduce the relative humidity to that within the cavities.
For cavity 103b, the outer heat seal 105 runs around the outer and inner peripheries of the annular dosing disc. There is also an outer moisture barrier 109 in the base 102. The channel 107 creates the inner barriers in the form of the inner heat seal 106 and the inner moisture barrier 110 in the base 102.
When the cavity 103a has been emptied, the inner heat seal 106 for that cavity becomes the outer heat seal 105 for cavity 103b thereby ensuring that the empty cavity 103b is not a source for moisture ingress.
This arrangement allows each cavity to be spaced from an adjacent cavity by as little as 1 mm. In this way, 60 cavities can be arranged on a dosing disc 101 with a diameter of 72 mm. A desiccant 108 (not shown) to dry the air in the channels 107 between components 111a, 111b and 112 sits on the underside of annular ring 111b (see
The annular ring 111a has a plurality of cavities 114 and the annular ring 111b has a plurality of cavities 115.
With this arrangement, it is not necessary to injection mould the annular rings such that there are separate channels as in
Claims
1. A support structure for a medicament comprising a base with at least one cavity for the medicament and a lid for sealing the medicament within the cavity, each moisture permeable region of the structure being protected against the ingress of moisture by locating a moisture absorbing sink between that region and the ambient air outside the structure, characterised in that each moisture permeable region comprises an inner moisture permeable barrier located adjacent to the cavity and an outer moisture permeable barrier, the moisture absorbing sink being located between the inner and outer barriers thereby reducing the relative humidity (RH) of the air passing through it to substantially the relative humidity (RH) of the air within the cavity so that there is minimal diffusion of moisture from the sink to the cavity.
2. A support structure as claimed in claim 1, wherein the base and the lid are moisture impermeable and the moisture permeable region of the structure is located where the lid is sealed to the base.
3. A support structure as claimed in claim 2, wherein the moisture absorbing sink between the lid and the base is spaced from the periphery of the cavity thereby forming an inner moisture permeable region and an outer moisture permeable region, the sink breaking the moisture ingress path so that there is minimal diffusion of moisture through the inner moisture permeable region to the cavity.
4. A support structure as claimed in claim 1, wherein the moisture absorbing sink comprises a channel in the base surrounding the cavity which contains dry air.
5. A support structure as claimed in claim 4, comprising a plurality of cavities each having a channel filled with dry air.
6. A support structure as claimed in claim 5, wherein each channel is connected to a single desiccant source which dries the air in all the channels.
7. A support structure as claimed in claim 1, wherein the moisture absorbing sink comprises a polymer ring surrounding the cavity and located between the lid and the base.
8. A support structure as claimed in claim 7, comprising a plurality of cavities each having a polymer ring.
9. A support structure as claimed in claim 2, wherein both the base and the lid have an aluminium layer for moisture impermeability, the lid being heat sealed to the base.
10. A support structure as claimed in claim 1, wherein the lid is moisture impermeable and the base material is moisture permeable, the moisture permeable regions being located where the lid is sealed to the base and within the base material of the cavity walls.
11. A support structure as claimed in claim 10, wherein a first moisture absorbing sink is located between the lid and the base and is spaced from the periphery of the cavity and a second moisture absorbing sink is located within the base material of the cavity walls thereby forming inner moisture permeable barriers and outer moisture permeable barriers, the sink breaking the moisture ingress path so that there is minimal diffusion of moisture through the inner moisture permeable barriers to the cavity.
12. A support structure as claimed in claim 10, wherein the moisture absorbing sink comprises a channel containing dry air surrounding the cavity opening where the lid is sealed to the base and passing through the cavity walls.
13. A support structure as claimed in claim 12, comprising a plurality of cavities each having a channel containing dry air.
14. A support structure as claimed in claim 13, wherein each channel is connected to a single desiccant source which dries the air in all the channels.
15. A support structure as claimed in claim 10, wherein the base is injection moulded and the lid has an aluminum layer for moisture impermeability, the lid being heat sealed to the base.
16. A support structure as claimed in claim 10, wherein the base comprises cooperating stackable elements, each element having a plurality of cavities, the cavities within one of the elements sitting between the cavities within another element when stacked, a moisture absorbing sink being formed by the spacing between the cooperating elements.
17. A support structure for a medicament substantially as herein described with reference to the accompanying drawings.
Type: Application
Filed: Jun 21, 2005
Publication Date: Jan 31, 2008
Inventor: Orest Lastow (Lund)
Application Number: 11/571,073